This invention relates generally to gas turbine engines and more particularly, to an in-line intercooler which eliminates removing the compressor main flow airstream from the compressor flowpath.
Gas turbine engines typically include a compressor for compressing a working fluid, such as air. The compressed air is injected into a combustor which beats the fluid, and the fluid is then expanded through a turbine. The compressor typically includes a low pressure compressor and a high pressure compressor.
The output of known gas turbine engines may be limited by the temperature of the working fluid at the output of the high pressure compressor, sometimes referred to as xe2x80x9cT3xe2x80x9d, and by the temperature of the working fluid in the combustor outlet, sometimes referred to as xe2x80x9cT41xe2x80x9d. To provide increased power output and cycle thermal efficiency without exceeding the T3 and T41 temperature limits, it is known to use an intercooler positioned in the fluid flow path between the low pressure compressor and the high pressure compressor.
Known intercoolers generally require the extraction and reintroduction of the entire gas turbine mainstream flow from and into the main gas turbine flowpath. Requiring that the entire gas turbine mainstream flow be extracted and reintroduced into the mainstream flow reduces the thermal efficiency of the cycle and adds component costs to an engine. Such intercoolers also introduce pressure losses associated with the removal of air, the actual cooling of that air, and ducting it back to the compressor. In addition, and in order to accommodate the entire mainstream flow, known intercoolers typically must have a large capacity. A significant amount of water is required by such high capacity intercoolers, and such high water consumption increases the operational costs. Of course, a larger capacity intercooler is more expensive, both to fabricate and operate, than a typical smaller capacity intercooler.
Also, it would be desirable to provide intercooling yet eliminate the requirement that the entire mainstream flow be extracted and reintroduced into the main gas turbine flow. It also would be desirable to reduce the required capacity for an intercooler yet provide substantially the same operational results.
These and other objects may be attained by a gas turbine engine including in-line intercooling wherein compressor intercooling is achieved without removing the compressor main flow airstream from the compressor flowpath. In an exemplary embodiment, a gas turbine engine suitable for use in connection with in-line intercooling includes a low pressure compressor, a high pressure compressor, and a combustor. The engine also includes a high pressure turbine, a low pressure turbine, and a power turbine.
For intercooling, fins are located in an exterior surface of the compressor struts in the compressor flowpath between the outlet of the low pressure compressor and the inlet of the high pressure compressor. Coolant flowpaths are provided in the compressor struts, and such flowpaths are in flow communication with a heat exchanger.
In operation, air flows through the low pressure compressor, and compressed air is supplied from the low pressure compressor to the high pressure compressor. The fins increase the heat transfer area between the gas turbine main compressor airflow and the coolant flow in the struts. Specifically, the flowpaths in the struts serve as heat sinks for cooling the high temperature compressor mainstream flow. The cooled airflow is supplied to the inlet of the high pressure compressor, and the highly compressed air is delivered to the combustor. Airflow from the combustor drives the high pressure turbine, the low pressure turbine, and the power turbine. Waste heat is captured by the boilers and the heat from the boilers in the form of steam is delivered to upstream components.
The in-line intercooling provides an advantage in that the temperature of the airflow at the outlet of the high pressure compressor (temperature T3) and the temperature of the airflow at the outlet of the combustor (temperature T41) are reduced as compared to such temperatures without intercooling. Specifically, the combination of the fins and coolant flow through the struts extract heat from the hot air flowing into and through the high pressure compressor, and by extracting such heat from the air flow, the T3 and T41 temperatures are reduced and compressive horsepower is reduced. Reducing the T3 and T41 temperatures provides the advantage that the engine is not T3 and T41 constrained, and therefore, the engine may operate at higher output levels than is possible without intercooling.